I need a subwoofer (ideally wireless) to add to some Energy Classic book shelf speakers to make out a 5.1 system. It'll be for HT and some music mostly at pretty low volume. All driven by an Onkyo tx-nr509

A friend of mine has a Polk PSWi-8m wireless sub that he'll sell me for $100. I've been unable to find any reviews and he's not local so I can't just swing by and listen to it. Apparently this thing comes bundled with some Mitsubishi TV's from what I can tell, but that's really all I know.